Trying to parse an impossible string results in a runtime exception

[Kaljurand]

Exception

java.lang.RuntimeException: Accessing the webservice failed: HTTP/1.1 500 -
    at ch.uzh.ifi.attempto.gfservice.gfwebservice.GfWebService.getEntity(Unknown Source)
    at ch.uzh.ifi.attempto.gfservice.gfwebservice.GfWebService.getResponseAsString(Unknown Source)
    at ch.uzh.ifi.attempto.gfservice.gfwebservice.GfWebService.parse(Unknown Source)

GF webservice console

GET /grammars/ACE-0_0_1.pgf [("command","parse"),("input","John"),("from","TestAttemptoGer")]
(500,"Internal Server Error",["src/server/PGFService.hs:(243,4)-(247,102):
    Non-exhaustive patterns in function jsonParseOutput\n"])

Not sure if the 500-error is intended here, but we might want/have to map it to a checked exception.